Breather plug for electric motors



June 29, 1943.

D. H. MANNEY 2/ f L I I Y 2 Sheets-Sheet 1 INVENTOR ATTCRHEYS- June 29,1943. D. H. MANNEY BREATHER PLUG FOR ELECTRIC MOTORS Filed Nov. 24, 19412 Sheets-Sheet 2 INVEYJTOR 0:? W0 H. MHN/YEY MWW- ATTORNEYS PatentedJune 29, 1943 2,323,146 BREATHER PLUG FOR ELECTRIC MOTORS David H.Manney, Dayton, Ohio, assignor to General Motors Corporation, Detroit,Mich, a corporation of Delaware Application November 24, 1941, SerialNo. 420,215

Claims.

This invention relates to an improved protective device for electricmachines and especially electric machines or electric motors used in asubstantially inflammable atmosphere in which fire or explosion mighttake place as a result of sparking in the machine or motor.

Electric machines and particularly electric motors are commonly used asdriving means for gas or gasoline pumps, apparatus in coal mines.

tion to provide an electric motor having a sealed casing or housing witha breather plug or plugs which establish communication between theinterior and exterior of the housing. The provision of such plugs thuseliminates the necessity of maintaining machine operations uponinter-fitting parts of the motor casing within such exceedingly closelimits, for the plugs in the present instance provide the breathchemicalworks or other plants where dustin er elements instead of the carefullydesigned laden air or atmosphere charged with infiamducts or spacesformed between inter-fitting mable or explosive gases or vapors areinvariparts of the motor housing. ably present. If an ordinary open typemotor The breather plugs of the present invention is used under suchcircumstances, the charged are made from a. sintered, non-compactedmetal atmosphere in and surrounding the motor may powder, presenting anindefinitely large numreadily be ignited by sparking at the brushes, berof small and tortuous paths or ducts through collector rings or anyother part oi the motor which atmosphere may be drawn into or ejectedcapable of an electric discharge tending to from the interior of themotor housing. These produce a spark, this 1535111? in muchldsimslugswith their small and totrtgous paths tor age and perhaps d as rous re orexp os on. no s prevent e propagationo ame from t e To avoid this,special motorsare available, these motor housing in case an inflammableor exmotors having casings or housing with predeplosive atmosphere orgas. drawn into and filltermined clearances between parts comprising ingthe motor, has been ignited by sparking the housing, said clearancesproviding communiwithin the motor housing. eating ducts between theinterior and exterior The character of the plugs and especially the ofthe housing which act as breather.openings tensil strength of the metalparticles comprisof such dimensions as to prevent flame propagaing theplugs are such that high resistance to tion from the interior ttlo theextgrior of the fracture, caused by pressure resulting either motorhousing in case e charge air or gas from explosion or freezing ofcondensed moiswithin the motor is ignited by sparking therein. turewithin the plug, is provided. Thus the To produce motors provided withsuch breathpossibility of reducing or even entirely destroyer spaces orducts between interfltting parts ing the protective function of abreather eleforming the otor usi requires careful and ment for thecasing of an electric motor such ed ou machining and working at closetoleras commonly used fibrous packing, porous plasn for if such spacesor ducts are too mall. tics, ceramics or porcelain and the like, whichexplosions Within th motor cannot p p rly are destructible and fragileunder conditions be relieved- The restriction ofl'ered by W1 mentioned,is substantially eliminated by the small duct/sor spaces would undulysubject the present type r plug which is adapted to wmb motor to theforces of the explosion therein. stand high pressure and continue itsprot'eb which would result m damage thereto and m 40 tive function underthe most adverse circumsome instances might even cause bursting ofstances. the motor casing thereby resulting in igniting The plugs of thepresent invention are adapt of the Surrounding charged atmosphere ed tobe used not only for the prevention or In case the spaces or ducts Justreferred to flame propagation but function also as drain are too large,proper impedance to flame propagauon would not be catered m which plugs,permitting condensed moisture to be stance the motor would of itself notbe damaged, ejected from within the casing and also as but again thetel-10L charged atmosphere ters for the lubricating system of thedevice. would be ignited. Thus it may be seen that such Further 013389and advantages of the esent breather spaces or clearances mustnecessarily 5o invenufln will be apparent from the following bemaintained within exceedingly close limits, requiring therefore tediousand careful machining of inter-fitting parts of the motor casing.

It is among the objects of the present invendescription, reference beinghad to the accompanying drawings wherein a preferred embodiment of thepresent invention is clearly shown. In the drawings:

Fig. 1 is a fragmentary sectional view of an electric motor equippedwith the present invention.

Fig. 2 is a longitudinal view. partly in section, showing the inventionapplied to another type of electric motor.

Fig. 3 is a fragmentary view of still another type of motor equippedwith the present invention.

Figs. 4 and 5 are enlarged sectional views showing the detailedconstruction of plugs comprising a body of sintered, non-compacted metalpowder.

Referring to the drawings and particularly to Fig. 1. the numeraldesignates the housing or casing oi the electric motor. Pole shoes 2|are supported within the housing carrying the field windings 22. A rotoror armature 23 is rotatably supported by the motor shaft 24 Journalledin sleeve bearings 26 and 28. said bearings being held in coaxialalignment within the housing 20 in any suitable manner.

The housing 20 has an inwardly extending cone-shaped shell portion 21forming an interior chamber which is in communication with the outsideof the motor housing through a neck or passage 28. This chambercomprises two compartments, the one designated by the numeral 29, whichmay be termed the lubricating oil reservoir," the compartment 30 whichmay be termed the sump" for the lubricant containing reservoir 29. Boththese compartments, the reservoir 29 and the sump 80. are incommunication with each other. Fibrous material of any suitable typedesignated by the numeral 80 is placed within these compartments, thisfibrous material being soaked with the lubricant, the fibrous materialin the sump acting as a wick to lift the lubricant from the sump up tothe reservoir. Openings in the bearings 25 and 26 permit this fibrousmaterial to contact with the exposed portion of the rotating armatureshaft 2! and thereby direct the lubricant upon the shaft. A duct 3iprovides communication between the reservoir compartment 29 and the sumpcompartment 30 so that lubricant flowing alon the shaft through thebearing 25 may enter duct 3|, flow therethrough and enter the sump 30from where said lubricant will again be lifted by the fibrous materialinto the reservoir 3|, thus creating a lubricant circulating system.With the bearing 25 in the opening of the coneshaped shell 21 and theshaft 24 in the bearing it may readily be seen that the interior of themotor casing 20 containing the field and armature and containing alsothe usual brushes or collector ring mechanism, not shown, in the presentdrawings, is completely shut oil or isolated from the chamber containingthe lubricant charged fibrous material Ii.

In the duct 3| there is provided a plug of the present invention, thisplug assembly being designated by the numeral 0. In the drawing it maybe seen that the plug is located in duct between the sump 30 and theother end of the duct which communicates with the reservoir portion 28through the clearance spaces provided between the bearing 25 and theshaft 24. This plug is of the type as designated in the Fig. 4 andcomprises a sleeve ll exteriorly threaded so as to be threadedlyreceived by the portion 42 oi. duct H. The sleeve ii is counterbored asat 43 to receive the. body of sinterednon-compacted metal powder N. Thisplug portion I may be formed from any number of metal powders such ascopper and tin powders, copper and nickel powder, iron powder and copperor other suitable powdered metals and may include small quantities ofnon-metallic materials such as graphite and the like. The method ofmaking such a porous metal plug is well known in the art and one of suchmethods is detailedly described in the Patent 2,198,702, issued to R. P.Koehring, April 30, 1940. Sumcient to say that the slntered,non-compacted metal plug 44 is of such a character that it providesindefinitely large number of small and tortuous paths or ducts throughwhich fluids may pass. Thus the presence oi this porous metal plug IIIin the oil conducting duct 8i of the motor acts as a filter for the oilpassing through duct It to the oil sump 20.

This porous, non-compacted metal plug 40 also acts as an arrester forpreventing the propagation of flame passing through the duct 3| towardthe oil containing sump 30 and reservoir 29 and in communication withthe outside of the metal through the neck or opening 26 normally closedby a Welsh plug 28a. If a motor is used in an installation surrounded ba charged atmosphere, that is, an atmsophere laden with an explosive orcombustible dust or gas, any ventllating air so charged and drawn intothe motor may readily be ignited by sparking of the brushes. collectorrings or any other part oi the electric motor capable of giving off aspark. Such explosion will, due to its pressure, tend to thrust theflame through any opening it may find, as for instance through theclearance space between the shaft 24 and the inner end of the bearing 26so that this flame could be directed into duct 3| and therethrough intothe lubricant containing chambers 29 and 30 if no impedance wereprovided in the duct. However, with the provision of the porous metalplug 40 in duct 3|, which provides innumerable small and tortuous paths,the propagation of th flame from duct 3i and its portion 42 through theplug 40 is entirely eliminated, for the small tortuous paths, will notpermit the flame to pass therethrough and into the lubricant containingchambers 3|] and 29. Thus the possibility of flame within the motorescaping to the exterior of the motor to ignite surrounding chargedatmosphere is substantially eliminated.

Another porous plug 50 is screw threadedly received in an opening it inthe casing 20 of the motor providing direct communication betwen theexterior of the motor and the interior portion thereof containing thefields, armature and brushes or collector ring mechanism thereof, Thisplug 60 is of the type shown in the Fig. 5 where a flanged collar 52,exteriorly threaded, has an elongated plug 53 made from sintered,non-compacted metal powder of the same character as plug Ill. This plug50 permits the motor to breathe ventilating air into its interior. andlike plug 40, prevents flame propagation from the interior of the motorto the exterior thereof in case an explosion occurs within the motor.Another plug 60 oi. the same type as plug 50, is provided in an opening62 at the bottom of the motor casing 20, this plug 60 providing an exitfor any condensed moisture that may gather at the bottom of the motor,this plug also preventing any flame propagation in case of an explosionwithin the motor.

From the aforegolng it may be seen that the motor as illustrateddn Fig.i has three porous metal plugs 40. and 80, all having a common function,that is the function of preventing flame propagation from the interiorof the motor to the exterior thereoi in case an explosion occurs withinthe motor. The plug ll acts also as an oil iilter and the plug III hasan additional function of providing a breather permitting ventilatingair to enter into the motor and the plug acting also as a drainpermitting any fluids present in the bottom of the motor casing toescape therefrom.

In Fig. 2 another type of electric motor is illustrated. This motor isadapted to be used as a driving element for gas or gasoline pumps, superchargers or the like. In driving gasoline pumps or super chargers amotor of this type forms a part of the equipment used on an airplane andin certain instances, especially when reaching high altitudes, issubjected to extremely low freezing temperatures. This motor comprises ahousing ll, an armature II, a commutator 12 thereof being provided withthe usual brush mechanism, not illustrated in the present instance. Thisarmature has a shaft 15 supported by two roller bearings 13 and Ilcarried in the housing. The end of the armature shaft 15 is connected tothe driven element which may be a gas pump, a supercharger or the like,said gas pump or supercharger sometimes giving ofl inflammable andexplosive gases which oittimes find their way along the shaft and intothe interior of the motor. Such gases within the motor are readilyignited by any sparking that might occur at the brush mechanism and insome instances an explosion within the motor takes place which, if theflame thereof is permitted to be propagated and find its way outside ofthe motor would cause explosions. In order to eliminate such flamepropagation, motors of this type are usually ventilated by a forced aircirculation being directed into the motor in any suitable manner. In theconstruction shown in Fig. 2, a duct 66 leads to the exterior of themotor and has a pipe 18 connected thereto which is connected to either asuction or a pressure pump adapted to draw air from the motor throughduct 65 or on the other hand force air through duct 65 into the motor.This duct 65 leads into a chamber l1 formed in the end housing 18 of themotor. In one end of said chamber the roller bearing II is provided. Inthis chamber there is provided also a porous metal plug Bil between ductis and bearing II, this plug comprising an outer sleeve II whichcontains the porous metal plug body ll! made from a sintered,non-compacted metal powder similar to the plugs 40 and 50 respectivelyshown in Figs. 4 and 5. An elongated tubular sleeve 83 extends throughthe porous metal plug 82, the shaft 15 of the armature extending throughthis elongated tube 88 which has a rotating fit about said shaft. A ductor passage 84 is provided on the outside of ball bearing 14, this ductconnecting the space on the inside of the bearing with the interior ofthe motor casing so that ventilating air passing from duct 85 throughthe porous plug 82 may enter the interior of the motor through duct 84instead of passing through the ball bearing H.

In any suitable location in the housing of the motor, preferablyadjacent the bottom thereof,

a plug I 50 is provided in an opening 85 in saidmotor housing this plugI50 being of the type illustrated in the Fig. and therefore having anelongated body made from a sintered non-compacted metal powder. The plugliil actsas an egress for the ventilating air of the motor casing whenthe pressure pump connected with pipe ll forces the air down into theduct ll. Where a suction pump is connected with pipe ll plug ill acts asan entrance for air into the interior of the motor casing II. In casesuch ventilating air is of an ble or explosive nature or in caseexploding gases find their way "from the mechanism driven by shaft itthrough the housing portion ll into chamber Il thereof and from thereare introduced into the interior of the motor by the forced ventilatingair, these two plugs l2 and ill will prevent flame propagation shouldsuch inflammable atmosphere within the motor be ignited by sparking atthe brushes on the commutator or any other place within the motor. i

In Fig. 3 is illustrated a fragmentary portion of a motor in which theair circulating mechanism in the form of a fan is within the motor anddriven by its rotating part directly. In this instance fan ill causesair to be drawn into the motor through a plug 9i like that shown in Fig.5 this air passes around the ileld windings II of the motor and otherparts to cool them and finally exiting from the interior of the electricmotor through plug ll identical with the plug shown in Fig. 4. Plugs 8iand 03 thus act as breathers capable of preventing any flame propagationresulting from an explosion within the motor housing.

The device shown in Fig. 2 is, as has been said, at times subjected tovery low freezing temperatures especially when the plane upon which itis used is traveling at high altitude. Any condensation which might takeplace within the motor and which might accumulate in plugs l2 and illwould be formed into ice in said plugs, the freezing of said moistureresulting in a terriflc pressure being exerted upon the particles makingup the porous plugs. Innumerable experiments have been made inconnection with these plugs, and during these experiments said plugswere laden with water and subjected to as low as 40 below zeroFahrenheit and in each instance no damage resulted. These tests alsoshowed this type of plug as being capable of withstanding extremely highpressure caused by the forcing of air or atmosphere therethrough due toan explosion. In none of these experiments to which these plugs weresubjected was the plug injured in any manner such as to prevent completeiunctioning thereof. Thus it may be seen that these porous plugs madefrom a sintered, non-compacted metal powder, are comparatively strong,being capable of withstanding extreme pressures such as are exerted incase of moisture within the plugs being frozen or the forcing ofatmosphere under pressure as the result of an explosion. Fibrousmaterials, prTr-ous plastics, ceramics or porcelain and the like whenused under such circumstances do not provide sufllcient strength towithstand the extreme pressure and tend to fracture or crack whensubjected thereto, thereby entirely destroying the function for whichthey are intended in any instance of this kind. Fracture of a plasticin.

any installation as disclosed in the drawing would necessarily permitflame propagation from the interior to the exterior oi the motor therebypermitting flames resulting from an explosion within the motor to bedirected exteriorly of the motor and ignite the surrounding inflammableor explosive atmosphere, thus resulting in a damaging and dangerous fireor explosion outside the motor.

while the embodiment oi the present invention as herein disclosed,constitutes a preferred form. it is to be understood that other iormsmight be adopted,.all coming within the scope of the claims whichfollow.

What is claimed is as follows:

i. In combination with an electric machine having a sealedcasing, of abreather plug in said casing adapted to prevent the propagation of flamecaused by the explosion of gas vapors ignited by sparking in theinterior of the casing. said breather plug comprising a body consistingof sintered, non-compacted metal powder.

2. In combination with an electric machine having a sealed casing. oi aporous metal plug in said casing providing for the transfer oi air intoand out of said casing. the draining of any moisture within the casingdue to condensation and for the prevention flame propagation caused bythe explosion oi gas vapors ignited by sparking within the casing of theelectric machine, said plug comprising an elongated body consisting ofsintered, non-compacted metal powder.

3. An electric machine having a casing providing bearings; an operatingshaft supported in said bearings; an oil reservoir in the casing; an oilsump in the casing; an oil conducting duct leading from one bearing incommunication with the reservoir to the sump; a porous metal plug insaid duct between the bearing and the sump for preventing thepropagation of time to the oil containing sump and for filtering theoil: and a second porous metal plug in the casing of the electricmachine, providing both a breather for said casing and a means forpreventing flame propagation caused by the explosions of gas vaporsignited by sparking in the interior of the electric machine, both oisaid poorus plugs being made train a sintered, non-compacted metalpowder.

4. In combination with an electric motor provided with a sealed casing,a duct leading into said casing for the introduction of a forced currentof air into the casing; second a duct in the casing providing for theegress of said air; a plug in each duct, each plug comprising a bodyconsisting of sintered, non-compacted metal powder providing anindefinitely large number of small and tortuous paths or ducts throughwhich the air passes and which prevent the propagation of flameresulting from the igniting of an inflammable or explosive atmospheredrawn into and filling the motor casing.

5. An electric motor having a casing at least a portion of whichcomprises a body consisting oi sintered, non-compacted metal powder saidportion of the casing providing a ventilator {or the motor whichprevents flame propagation.

DAVID H. MANNEY.

